Embodiments of the present disclosure generally relate to an energy exchange system for conditioning air in an enclosed structure, and more particularly, to a system and method for adjusting, varying, or otherwise controlling parameters of a liquid desiccant within the energy exchange system.
Enclosed structures, such as occupied buildings, factories and the like, generally include a heating/ventilation/air conditioning (HVAC) system for conditioning outdoor ventilated and/or recirculated air. The HVAC system typically includes a supply air flow path and an exhaust air flow path. The supply air flow path receives pre-conditioned air, for example outside air or outside air mixed with re-circulated air, and channels and distributes the pre-conditioned air into the enclosed structure. The pre-conditioned air is conditioned by the HVAC system to provide a desired temperature and humidity of supply air discharged into the enclosed structure. The exhaust air flow path discharges air back to the environment outside the structure. Without energy recovery, conditioning the supply air typically requires a significant amount of auxiliary energy, particularly in environments having extreme outside air conditions that are much different than the required supply air temperature and humidity. Accordingly, energy exchange or recovery systems are used to recover energy from the exhaust air flow path.
Conventional energy exchange systems may utilize energy recovery devices (for example, energy wheels and permeable plate exchangers) or heat exchange devices (for example, heat wheels, plate exchangers, heat-pipe exchangers and run-around heat exchangers) positioned in both the supply air flow path and the return air flow path. Liquid-to-air membrane energy exchangers (LAMEEs) may be fluidly coupled so that a desiccant liquid flows between the LAMEEs in a run-around loop, similar to run-around heat exchangers that typically use aqueous glycol as a coupling fluid.
Typically, a conventional HVAC system is sized depending on cooling, heating, and ventilation peak loads of a particular enclosed structure. In some systems, a constant air volume is supplied to each room within an enclosed structure. As such, a temperature of the air supplied to each room is generally similar. In other systems, the air volume may be varied, through dampers, supply paths, exhaust paths and the like. For example, output from cool and warm air paths may be mixed in order to vary the temperature of a particular room.
Typically, however, while known systems may be able to vary temperature within separate and distinct rooms, zones, or spaces, humidity generally cannot be independently controlled. Yet, different rooms, zones, or spaces may have different humidity levels based on latent loading (for example, the number of people within each particular zone), and/or different humidity level requirements. Yet, in known systems, when humidity is varied, the humidity level of all of the rooms is generally changed accordingly. Additionally, known systems may utilize relatively high levels of energy in order to alter temperature and/or humidity. Further, known systems typically cool air to dew point in order to remove moisture. As such, in order to alter humidity levels, the air supplied to a room may be lower than desired, and may often require an additional heating device to raise the level of supplied air. Because additional heating devices may be used, more energy may be used to condition the air that is supplied to the room.